JP3932967B2 - Fuel injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device (hereinafter, “fuel injection device” is referred to as an injector) that reduces the rate of change in fuel injection amount even when a contact portion of a valve member seated on a conical surface of a valve body is worn.
[0002]
[Prior art]
The inner circumferential wall of the valve body has a conical surface whose diameter decreases in the direction of fuel flow toward the nozzle hole, and the contact portion of the valve member is seated on the conical surface to block fuel injection from the nozzle hole, 2. Description of the Related Art An injector that injects fuel from an injection hole by being separated is known. As the shape of the contact portion seated on the conical surface of the valve body, for example, a corner portion formed by taper surfaces (hereinafter, “corner portion formed by taper surfaces” is simply referred to as a corner portion), As disclosed in Japanese Patent Application Laid-Open No. 8-218973, one having a spherical shape is known.
[0003]
FIGS. 4A and 4B show an injector seated on the conical surface 202 with a convex curved surface 214. The tip of the valve member disclosed in JP-A-8-218973 is spherical and the entire tip is spherical, but the entire tip of the valve member 210 is not spherical. However, the convex curved surface 214 constitutes a part when the entire tip of the valve member 210 is a spherical surface. Since the spherical center of the spherical surface of the tip of the valve member formed in a spherical shape is on the central axis of the valve member, the radial center O of the convex curved surface 214 is also on the central axis 220 of the valve member 210. Since the convex curved surface 214 forms a part of a spherical surface, the radius r of the convex curved surface 214 is determined by the seat diameter ds and the seat angle θ of the conical surface 202.
[0004]
When the valve member is separated from the conical surface, the throttle position of the opening channel formed between the conical surface and the abutting portion is determined by the seat position where the distance between the abutting portion and the conical surface is the smallest. Instead, the channel area of the opening channel formed in a ring shape in the circumferential direction is determined at a minimum. As shown in FIG. 4, in the injector that contacts the conical surface 202 formed on the inner peripheral wall of the valve body 200 with the convex curved surface 214 formed on the contact portion 212 of the valve member 210, the contact portion 212 is the conical surface 202. When the seat diameter is the same, the throttle position of the opening channel formed between the conical surface 202 and the contact portion 212 when the seat is separated from the corner is conical at the corner depending on the angle of the corner. In general, it is farther from the fuel upstream side, that is, from the central shaft 220 of the valve member 210, as compared with the injector that contacts the fuel. Therefore, if the lift amount is the same, the flow path area at the throttle position is larger when the contact portion of the valve member is spherical than at the corner portion.
[0005]
In addition, the rate of increase of the flow path area from the throttle position toward the upstream side and the downstream side is larger when the contact portion is a spherical surface than the corner portion. The channel resistance of the open channel formed between the contact portion and the contact portion is spherical is smaller than the corner portion.
If the lift amount and the seat diameter are the same, the pressure loss of the opening flow path is smaller than that of the spherical contact portion, and the fuel injection pressure injected from the injection hole increases. Therefore, the fuel can be atomized and injected.
[0006]
[Problems to be solved by the invention]
In the injector shown in FIG. 4, when the contact portion 212 repeats seating and separation with the conical surface 202, the contact portion 212 is worn as indicated by a two-dot chain line in FIG. 4B. Then, the throttle position of the opening flow path formed between the conical surface 202 and the contact portion 212 with respect to the wear amount δ moves to the fuel downstream side, that is, the central shaft 220 side, and the maximum lift amount of the valve member 210 is increased. growing. When the wear amount δ of the contact portion 212 increases, the flow rate of fuel flowing between the contact portion 212 and the conical surface 202, that is, the fuel injection amount injected from the injection hole 204, changes compared to before the wear.
An object of the present invention is to provide an injector having a small rate of change in fuel injection amount even when the contact portion is worn in a configuration in which the contact portion of the valve member is seated on the conical surface of the valve body as a convex curved surface. .
[0007]
[Means for Solving the Problems]
According to the injector of the first aspect of the present invention, the contact surface of the contact portion of the valve member seated on the conical surface of the valve body is a convex curved surface. Since the fuel injection pressure increases as compared with the injector whose corners are seated on the conical surface, the fuel injected from the injection hole can be atomized.
[0008]
Further, the radius center of the convex curved surface at the contact position with the conical surface is located on the far side from the central axis of the valve member as viewed from the contact position. In other words, when the seat diameter when the convex curved surface is seated on the conical surface and the seat angle formed by the conical surface are the same, the convex curved surface is compared with the spherical surface whose radius center is located on the central axis of the valve member. The radius of is large. The radius of the convex curved surface is set regardless of the sheet diameter and the sheet angle.
[0009]
When the radius of the convex curved surface that comes into contact with the conical surface is increased, the amount of change in the lift amount of the valve member is reduced even if the contact member wears due to repeated seating and separation of the valve member with the conical surface. In addition, when the contact portion is separated from the conical surface and the throttle position of the opening channel formed between the contact portion and the conical surface moves due to wear of the contact portion, the radius of the convex curved surface As the value increases, the amount of movement of the aperture position decreases. Therefore, if the wear amount of the contact portion is the same, the larger the radius of the convex curved surface, the lower the rate of change of the fuel flow rate, that is, the fuel injection amount that flows through the open flow path. Here, the rate of change of the fuel flow rate or the fuel injection amount represents the ratio of the increase or decrease in the fuel flow rate or the fuel injection amount that has changed due to wear with respect to the fuel flow rate or the fuel injection amount before wear.
Further, by increasing the radius of the convex curved surface, the gap formed between the convex curved surface and the conical surface is reduced, so that it is difficult for foreign matter to get caught between the convex curved surface and the conical surface. Therefore, fuel can be prevented from leaking from between the valve member and the valve body due to the biting of foreign matter.
[0010]
According to the injector of the first aspect of the present invention, the valve member has a cylindrical surface extending from the upstream end of the convex curved fuel toward the anti-injection hole along the central axis direction of the valve member. When the diameter is D and the radius of the convex curved surface is r, the rate of change of the fuel flow rate flowing through the open flow path formed between the contact portion and the conical surface is 3% or less even if the contact portion is worn. Thus, the radius r of the convex curved surface is set to 0.53D ≦ r. By increasing the radius of the convex curved surface, the rate of change of the fuel injection amount can be reduced even if the contact portion is worn.
[0011]
If the radius of the convex curved surface of the contact portion is increased, the lift amount due to wear and the change amount of the throttle position in the opening channel are reduced, and the rate of change of the fuel injection amount can be reduced. However, if the radius of the convex curved surface of the contact portion is increased to reduce the rate of change of the fuel injection amount too much, the flow resistance of the open flow path increases and the pressure loss increases. Then, fuel injection pressure falls and atomization of injected fuel is impaired. According to the injector of the second aspect of the present invention, the radius of the convex curved surface is set so that the rate of change of the fuel flow rate flowing through the opening channel is 1% or more and 3% or less even if the contact portion is worn . Therefore, the change rate of the fuel injection amount is reduced and the fuel injection pressure is prevented from decreasing. Therefore, the injected fuel can be atomized.
[0013]
According to the injector of claim 3 of the present invention, the valve member has a cylindrical surface extending from the fuel upstream side end of the convex curved surface toward the anti-injection hole side along the central axis direction of the valve member, and the outer diameter of the cylindrical surface is reduced. D, where r is the radius of the convex curved surface, 0.53D ≦ r ≦ D. By setting the maximum value of the radius of the convex curved surface, the fuel injection pressure is prevented from decreasing. Therefore, the injected fuel can be atomized.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, examples showing embodiments of the present invention will be described with reference to the drawings.
An injector according to one embodiment of the present invention is shown in FIG.
The valve body 12 is fixed to the fuel injection side end inner wall of the valve housing 16 by welding. The valve body 12 has a conical surface 13 whose diameter is reduced toward the nozzle hole 14 side in the fuel flow direction on the inner peripheral wall.
As shown in FIG. 1, the valve member 20 has an abutting portion 21 seated on the conical surface 13 at an end portion on the injection hole 14 side. When the contact portion 21 is seated on the conical surface 13, the fuel injection from the nozzle hole 14 is blocked, and when the contact portion 21 is separated from the conical surface 13, fuel is injected from the nozzle hole 14.
[0015]
The contact surface of the contact portion 21 seated on the conical surface 13 is a convex curved surface 22 constituting a part of a spherical surface. Therefore, the curvature of the entire convex curved surface 22 is equal. The center O of the radius r of the convex surface 22 is located on the other side of the central axis 100 of the valve member 20 when viewed from the contact position of the convex surface 22 that contacts the conical surface 13. The radius of the convex curved surface 22 is larger than when the tip of the valve member on the injection hole side is spherical. A cylindrical surface 23 extends from the upstream end of the convex curved surface 22 along the central axis 100 of the valve member 20 toward the anti-injection hole.
[0016]
As shown in FIG. 2, the tubular member 30 is inserted into the inner wall of the valve housing 16 on the side opposite to the injection hole, and is fixed to the valve housing 16 by welding. The cylindrical member 30 includes a first magnetic cylindrical portion 32, a nonmagnetic cylindrical portion 34, and a second magnetic cylindrical portion 36 from the nozzle hole 14 side. The nonmagnetic cylinder portion 34 prevents a magnetic short circuit between the first magnetic cylinder portion 32 and the second magnetic cylinder portion 36.
[0017]
The movable core 40 is formed of a magnetic material in a cylindrical shape, and is fixed to the end portion 24 of the valve member 20 on the side opposite to the injection hole by welding. The movable core 40 reciprocates together with the valve member 20. The outflow hole 42 that penetrates the cylindrical wall of the movable core 40 forms a fuel passage that communicates the inside and outside of the cylinder of the movable core 40.
[0018]
The fixed core 44 is formed of a magnetic material in a cylindrical shape. The fixed core 44 is inserted into the cylindrical member 30 and is fixed to the cylindrical member 30 by welding. The fixed core 44 is installed on the side opposite to the injection hole with respect to the movable core 40 and faces the movable core 40.
[0019]
The adjusting pipe 46 is press-fitted into the fixed core 44 and forms a fuel passage therein. The spring 48 is locked to the adjusting pipe 46 at one end and is locked to the movable core 40 at the other end. By adjusting the press-fitting amount of the adjusting pipe 46, the load of the spring 48 applied to the movable core 40 can be changed. The movable core 40 and the valve member 20 are biased toward the conical surface 13 by the biasing force of the spring 48.
[0020]
The coil 50 is wound around the spool 52. The terminal 55 is insert-molded in the connector 54 and is electrically connected to the coil 50. When the coil 50 is energized, a magnetic attractive force acts between the movable core 40 and the fixed core 44, and the movable core 40 is attracted toward the fixed core 44 against the urging force of the spring 48.
[0021]
The filter 60 is installed on the fuel upstream side of the fixed core 44 and removes foreign matters in the fuel supplied to the injector 10. The fuel that has flowed into the fixed core 44 through the filter 60 flows between the fuel passage in the adjusting pipe 46, the fuel passage in the movable core 40, the outflow hole 42, and the inner peripheral wall of the valve housing 16 and the outer peripheral wall of the valve member 20. Pass through sequentially. When the valve member 20 is separated from the conical surface 13, the fuel passes through an opening channel formed between the contact portion 21 and the conical surface 13 and is guided to the injection hole 14.
[0022]
The energization of the coil 50 is interrupted and the injector 10 intermittently injects, whereby the abutting portion 21 repeats the seating and separation with the conical surface 13. Thereby, the contact part 21 is worn. When the contact portion 21 wears, the lift amount of the valve member 20 increases, and the throttle position of the opening flow path moves to the fuel downstream side, so that the fuel flow rate, that is, the fuel injection amount that flows through the opening flow path changes. However, the radius r of the convex curved surface 22 of the contact portion 21 is not determined by the seat diameter ds and the seat angle θ of the conical surface 13, and is set larger than the spherical surface having the radius center O on the central axis 100. Thus, the rate of change of the fuel flow rate flowing through the opening channel, that is, the rate of change of the fuel injection amount decreases with respect to the amount of wear of the contact portion 21.
[0023]
FIG. 3 shows the relationship between the radius r of the convex curved surface 22 and the rate of change of the fuel flow rate through the open flow path when the seat diameter ds is 1.4 mm and the outer diameter D of the cylindrical surface 23 is 1.5 mm. It can be seen that the rate of change of the fuel flow rate decreases as the radius r increases. In order to make the rate of change 3% or less, it is desirable that 0.53D ≦ r.
[0024]
When the radius r of the convex curved surface 22 is increased, the change rate of the fuel flow rate is reduced, but the flow resistance of the open flow path is increased and the fuel injection pressure is decreased. In order to suppress a decrease in fuel injection pressure while suppressing a decrease in fuel flow rate change rate, the fuel flow rate change rate is preferably 1% or more and 3% or less.
[0025]
In the present embodiment, by increasing the radius of the convex curved surface 22, the gap formed between the convex curved surface 22 and the conical surface 13 is reduced, so that a foreign object bites between the convex curved surface 22 and the conical surface 13. It becomes difficult to get in. Therefore, since foreign matter is caught, fuel can be prevented from leaking from between the valve member 20 and the valve body 12.
In the present embodiment, the convex curved surface 22 constitutes a part of a spherical surface, and the curvature of the entire convex curved surface 22 is equal, but may be a convex curved surface having different curvatures.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the vicinity of an injection hole of an injector according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an injector according to the present embodiment.
FIG. 3 is a characteristic diagram showing the relationship between the seat diameter and the flow rate change rate in this example.
FIG. 4 is a cross-sectional view showing the periphery of an injection hole of a conventional injector.
[Explanation of symbols]
10 Injector (fuel injection device)
12 Valve body 13 Conical surface 14 Injection hole 20 Valve member 21 Contact part 22 Convex surface 40 Movable core 44 Fixed core

Claims (3)

A valve body having a conical surface whose diameter decreases in the fuel flow direction toward the nozzle hole;
A valve member having a contact portion that closes the nozzle hole by sitting on the conical surface and opens the nozzle hole by sitting away from the conical surface;
A fuel injection device comprising:
The contact surface of the contact portion seated on the conical surface is a convex curved surface, and the radius center of the convex curved surface at the contact position with the conical surface exceeds the central axis of the valve member as viewed from the contact position. The valve member has a cylindrical surface extending from the fuel upstream end of the convex curved surface toward the anti-injection hole along the central axis direction of the valve member, and the outer diameter of the cylindrical surface is D, where r is the radius of the convex curved surface, the rate of change of the flow rate of fuel flowing between the abutting portion and the conical surface that wears by repeated seating and separation with the conical surface is 3% or less. Thus, the radius r of the convex curved surface is set to 0.53D ≦ r . The radius r of the convex curved surface so that the rate of change of the flow rate of fuel flowing between the abutting portion and the conical surface that wears by repeated seating and separation with the conical surface is 1% or more and 3% or less. The fuel injection device according to claim 1, wherein is set. The fuel injection device according to claim 1, wherein 0.53D ≦ r ≦ D.

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